148 



FOSSII, TURTLES OF NORTH AMERICA. 



laterally. The distal end of a costal bone is 70 mm. wide. The surface of the bones is usually 

 moderately smooth, but markt by irregular, rather straight, vascular grooves. The sulci are 

 usually quite distinct. 



The nuchal scute is present, as stated. Its lateral extent is conjectural; the fore-and-aft 

 width is about 30 mm. The widths of the vertebral scutes can not be exactly determined; 

 but they all appear to correspond closely to those of O. gibbi Wieland. The first evidently 





vJ 



176. j 



'77- 



178. 



'79- 



'75- 



FIGS. 175-180. Osteopygis platylomus. Peripherals and sections. 

 Type. Xi. 



175. Sixth, seventh, and eighth right peripherals. 



176. First, second, third, and fourth right peripherals. 



177. Sections of first and second left peripherals, a, distal end of second; b, 



proiimal end of second; c, near proximal end of first. 



178. Hinder end of eighth peripheral. 



179. Front end of eighth peripheral. 



180. Section along right articular border of the pygal. 



extended laterally to about the middle of the first peripheral. The 

 eleventh reacht laterally the hinder border of the pit for the last rib. 

 The costo-marginal sulci run along on the upper borders of the first and second peripherals, 

 then disappear, to reappear on the upper borders of the eighth to the eleventh. From the 

 third to the eighth peripherals the sulci occupied doubtless the space between the costals and 

 the peripherals. 



At present there remain of the plastron only a part of the left hyoplastron, most of the left 

 hypoplastron, and most of the right xiphiplastron. The plastron seems not to have differed 

 in any important way from that of O. borealis. Evidently there was a fontanel between the 

 hyoplastra in front and the hypoplastra behind. At the narrowest part of the bridge the hypo- 

 plastron is 58 mm. wide. The thickness at the inguinal notch is 16 mm. No sulci are to be 

 seen on these bones, except a faint one near the base of the xiphiplastron. To the present 

 writer it seems evident that the bones on the right of Cope's figure of the plastron of this species 



